[ODE] Mixing WorldStep, QuickStep and/or StepFast

[Megan Fox]

Speaking from a bit of personal experience, trying to mix fast-step and
world-step reliably will lead only to pain and suffering.  To make fast-step
work reliably requires making sacrifices and tweaks which tend to make
world-step unhappy, and vice versa.  (every time I switched between them in
my test app, I had to go through re-balancing all of my masses and forces to
look right)

On the other hand, it does seem as if it might be possible to use quick and
world step interchangably, depending on needs at the time.  While quick-step
does tend to knock over tall piles, it behaves admirably under most other
conditions, and is just about as good as world-step in standard scenes.


Only thing to be wary of is that quick-step will jostle tall (>4 or so)
piles of boxes down, so if you for some reason have a region heavy in tall
stacks, switching to quick-step would result in those stacks falling over.
Then again, stacks cause world-step to slow down dramatically, so you
probably wouldn't have them anyways.


Just my 2c

-Megan

> Is it possible / does it make sense mixing the precise-but-expensive
> WorldStep with the approximate-but-fast methods?
>
> What I'm thinking is a game, say with a 60Hz physics update, where good
> framerates are more important than perfect accuracy. The idea would be
> to do a WorldStep every 10 frames and do QuickStep or StepFast in the
> frames in between, to keep the error from accumulating too much.
>
> Note that this is purely speculative since physics aren't currently
> having any performance effect in my prototype, and I'm fully aware one
> shouldn't optimize prematurely, but the idea crossed my mind and I
> wanted to ask :)
>
> 	--Gabriel
>
>
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